It is well known that viruses naturally deliver nucleic acids to cells and have therefore been exploited as gene delivery vehicles. However, in order for a recombinant virus to delivery a nucleic acid to a cell, the virus must first have access to the cell. Circulating virus in a mammal may not have ready access to cells to which it is desired that a nucleic acid be delivered. The present invention provides a means of providing to a virus access to cells to which it is desired that a nucleic acid be delivered.
The recent cloning of full length cDNAs for gene products implicated in several muscular dystrophies (Lim et al., 1995, Nature Genetics 11: 257-265; Piccolo et al., 1995, Nature Genetics, 10: 243-245; Nigro et al., 1996, Nature Genetics 14: 195-198; Bonnemann et al., 1995, Nature Genetics 11: 266-273; and Helbling-Leclerc et al., 1995, Nature Genetics 11: 216-218) has been paralleled by improvement in a variety of virus-based vector systems for use in somatic gene transfer (Yang et al., 1994, Nature Genetics 7: 362-369; Yeh et al. 1996, J. Virology 70: 559-565; and Wilson, 1996, New Eng. J. Med. 334:1185-1187). The universal muscle involvement and resulting respiratory insufficiency in these diseases have focussed attention on the need for systemic vector delivery in vivo to animal tissues and organs (Boland et al., 1996, Pediatric Neurology, 14: 7-12; Stedman et al., 1991, Nature 352: 536-539.; Schlenker et al., 1991, J. Appl. Physiol. 71: 1655-1662; and Smith et al., 1987, New Engl. J. Med. 316: 1197-1205). Under physiologic conditions, the continuous endothelium of the skeletal muscle microvasculature is virtually impermeable to proteins larger than albumin (Stokes radius 3.5 nanometers; Berne et al., 1992, In: Physiology, Mosby, St. Louis), and the underlying basal lamina restricts the diffusion of larger macromolecular aggregates (Majno et al., 1961, J. Biophys. Biochem. Cytol. 11:571-597).
There is an acute need to develop compositions and methods which facilitate access of large macromolecules to muscle for the purposes of delivery of compounds which are of therapeutic benefit to mammals in need of such compounds. The present invention satisfies this need.